Various conveyor systems are known to the prior art. Such systems typically consist of a series of track segments which are joined together along their ends to form a pathway for one or more trolleys. In the past, it was common to weld the various track segments together when the conveyor system was installed on site. U.S. Pat. No. 3,559,585 (Lempio) is illustrative of this technology. There, a power and free type conveyor system is disclosed which consists of an upper track of C-shaped cross-section, and a lower track of U-shaped cross-section. The upper and lower tracks consist of longitudinal track segments that are welded together in an end-to-end fashion by conventional methods. The upper track supports an endless driven chain which is provided with pushers projecting through the downward facing slot in the upper track. The lower track supports load carrying trolleys which are propelled by the pushers. The upper and lower tracks are welded to inverted U-shaped yokes which add rigidity to the two tracks and help to maintain a proper spacing between them.
While conveyor systems such as that described in U.S. Pat. No. 3,559,585 (Lempio) have many desirable features, these systems rely heavily on welding to secure the yokes to the track segments and to join the ends of abutting track segments together across a joint. However, it is frequently necessary to change the configuration of conveyor systems after they have been installed at a customer facility. In auto assembly plants, for example, the configuration of conveyor systems is generally changed each year, if not more frequently, to accommodate the manufacture of newer models of automobiles. Therefore, conveyor systems that rely heavily on welding are undesirable, since reconfiguration or disassembly of such a system is difficult, costly, and time consuming, and results in the scrapping of component parts that are damaged during disassembly. There is thus a need in the art for a conveyor system that may be easily assembled or disassembled without welding, and which is constructed of component parts that may be removed from the system without damage and incorporated into other conveyor systems.
To this end, various conveyor systems have been developed which require less welding during assembly. Thus, U.S. Pat. No. 4,811,829 (Nakazawa et al.) describes a frame for a passenger conveyor which consists of a plurality of frame members. This system is designed to preserve the exact spatial relation of the component parts each time the system is disassembled and reassembled. In this system, adjoining frame members are secured to each other during assembly at the plant through the use of bolts inserted through holes provided in adjoining mounting seats (see FIG. 3). A positioning pin is then inserted into a hole in the side of one of the frame members, and the base of the pin is welded to the opposite frame member. When the frame is reassembled at the installation site, the positioning pin ensures that the original alignment of the opposing frame members is reproduced.
While the system disclosed in U.S. Pat. No. 4,811,829 (Nakazawa et al.) ensures a certain reproducibility in assembly that may be important in some applications, installation of the system still requires some welding. Furthermore, the individual component parts of this system are unique by design, and cannot be interchanged. As a result, systems of this type are expensive to manufacture and maintain.
U.S. Pat. No. 4,467,914 (Trammel et al.) discloses a conveyor system which does not require welding. Instead, the system utilizes anchor wedges and flanges to properly align and join adjacent conveyor trough segments. The abutting ends of the segments are secured together by means of opposing rectangular flanges. The flanges are provided with holes for accommodating bolt and nut assemblies that are used to secure the opposing flanges together. Each segment is further provided with a channel which runs along its length and which runs underneath the rectangular flanges. In use, the anchor wedge, which is complimentary in shape to the channel, is inserted into the channel and driven forward so that it spans the abutment, thereby holding the abutting portions in proper alignment while they are secured together.
However, while the system of U.S. Pat. No. 4,467,914 (Trammel et al.) is advantageous in some respects, systems of this type are difficult to disassemble, since the anchor wedges must be forcibly removed from each channel in the process. Furthermore, insertion or removal of the anchor wedges may cause the track to be damaged, particularly when the track is constructed from aluminum, plastic, and other lightweight materials.
More recently, splice bars have been developed to join abutting track segments without the need for welding. Thus, U.S. Pat. No. 4,733,771 (Grundken et al.), U.S. Pat. No. 4,646,905 (Grundken et al.), U.S. Pat. No. 4,420,075 (Skolik et al.), and U.S. Pat. No. 4,157,751 (Grundken et al.) disclose special dogbone-shaped splice bars which are used to join abutting track segments in conveyor systems designed for use in mines. However, since these splice bars are designed to permit a certain amount of angular mobility, they are not suitable in many applications. Furthermore, the odd shape of these splice bars increases their manufacturing expense, and requires special tooling on the track segments.
A more satisfactory splice bar is shown in U.S. Pat. No. 4,951,809 (Boothe et al.). There, a conveyor system is disclosed which uses splice bars of a standard rectangular shape. The conveyor system consists of a plurality of track segments wherein each segment is provided with longitudinal twin channels of T-shaped cross section. The channels are open, but are provided on each side with a flange that protrudes partially into the opening. Adjoining track segments are connected to each other by rectangular splice bars which are disposed in the channels and which span the abutment. The splice bars are provided with threaded apertures, and are held in place by a metal plate provided with a series of holes which is placed over the abutment. Threaded bolts are provided which may be inserted into the holes to engage the threaded apertures in the splice bar, thereby clamping the abutting members together.
A further problem with many prior art conveyor systems is that they are not readily adaptable to restrictions in conveyor configurations imposed by design constraints. For example, in U.S. Pat. No. 4,467,914 (Trammel et al.), the support members are designed to be bolted onto the flanges, thus limiting the user to particular track configurations which may not be suitable for a given installation site. For instance, the placement of equipment around the conveyor system may introduce interferences in the placement of the support members. This would require the support members to be displaced from the flanges and welded to the side of the conveyor system.
It is thus desirable in a conveyor system for the placement of the support members to be adjustable along the length of the conveyor. One such system is shown in U.S. Pat. No. 5,137,145 (Clopton). There, a conveyor system is disclosed having individual track members which are provided with channels and which have lips that protrude partially across the channels, causing the channels to be T-shaped in cross-section. A special attachment member, shown in FIG. 9, is provided with opposing prongs that engage the lips of opposing track members, thereby securing them together from the interior. Support brackets may be attached to the track members by a bolt whose flat, irregularly shaped head is disposed in one of the longitudinal channels in the track member. However, while the system disclosed in U.S. Pat. No. 5,137,145 (Clopton) is advantageous in some respects, the means disclosed therein for allowing the support members to be adjustably positioned along the length of the track is undesirable in that it requires special bolts which increase the manufacture and maintenance costs of the system.
Yet another problem with prior art conveyor systems is their extensive use of steel and other heavy and expensive materials. Such materials contribute directly to the cost of manufacturing, shipping, and assembling conveyor systems. In an effort to avoid these pitfalls, some conveyor systems have been developed using lightweight materials. Thus, U.S. Pat. No. 5,178,263 (Kempen) discloses modular track sections for an endless conveyor. The sections are made from high molecular weight plastic and are I-shaped in transverse cross-section. Each side of the track includes a longitudinal slot running the length of the track. A stainless steel mounting rail is disposed in each slot to strengthen the track. The mounting rail spans the abutment of adjoining track segments and is provided with a series of holes for receiving threaded bolts, thereby allowing the track segments to be joined together. A plurality of vertically disposed hangers are provided which allow the track to be supported from vertical posts.
While the references noted above disclose some features which are desirable for conveyor systems, however, none of these references disclose a convenient means for attaining variable track drops. In a conveyor system, such track drops are important, for example, to prevent runaway of carriers on a decline, and to facilitate wide wing transfer of carriers between tracks. In the past, track drops have been accomplished by custom designed track segments which add significantly to the cost and maintenance of the conveyor system, and detract from its versatility.
It is thus an object of the present invention to provide a conveyor system which avoids the aforementioned infirmities in the prior art, and which is provided with a convenient means for attaining variable track drops.
It is a further object of the present invention to provide a conveyor system in which the track segments may be releasably fitted together in an end-to-end fashion without welding and through the use of ordinary hand tools.
It is yet another object of the present invention to provide a conveyor system in which the support members may be releasably attached to the track without welding and through the use of ordinary hand tools.
It is another object of the present invention to provide a conveyor system in which the support members may be variably positioned along the length of the track.
It is still another object of the present invention to provide a conveyor system which is made out of lightweight materials which avoid the manufacture, distribution, and installation costs incurred through the use of steel and other heavy materials in a conveyor system, without sacrificing the strength and durability afforded by those materials.
These and other objects are achieved by the present invention, as hereinafter disclosed.